The CSS revisions were not removed with 3.8.1, and should still be there.

Your custom CSS changes are stored in the *_options table of your database. Each custom CSS revision is stored as a post using a custom CSS post type named safecss. As a result, your changes won't disappear, even if you delete the jetpack plugin.

Your CSS changes are stored in the *_posts table, along your Posts, Pages, and other Custom Post Types.
Custom CSS revisions use the safecss post_type and post_title, so you should be able to find them by filtering all posts with this Post title.